Work vehicles such as tractors and crawlers have the capability to tow various pulled implements. The implements may be, for example, storage carts, planters, sprayers, tillers, etc. Such work vehicles typically have a drawbar pivot point for the attachment of a load bearing member such as a drawbar which is in turn attached to the pulled implement. Many of the pulled implements are very heavy, resulting in strain on the engine and chassis of the work vehicle. In order to determine the load of the implement on the work vehicle for implement or vehicle adjustment or measurement, it is desirable to measure the side, vertical, and draft load placed on the work vehicle by the mobile implement. Measuring strain on different dimensions is useful for other purposes such as draft control to control the draft force of the pulled implement by changing operating depth.
Presently, the strain gauges may sense strain in one direction, possibly compensating for strain in other directions or environmental effects. Typically such gauges are based on four resistors in a Wheatstone bridge configuration. One, two, or all of the resistors of the "bridge" are strain gauges. The change in voltage across the "bridge" is proportional to the change in resistance due to the strain placed on the gauge or gauges. The resulting voltage output signal represents the strain. The signal is then amplified and filtered to obtain a representation of the strain value. Typically, the Wheatstone bridge is configured to sense reactions from loads in only one direction.
Thus, such bridges have limited utility because they cannot differentiate strain in multiple directions. Additionally, the gain involved in amplifying such a signal is limited by common mode noise from the power source thus restricting strain sensing ability. Finally, temperature affects the strain measurements by changing resistance in the gauge from thermal strain in the material.
Therefore, it would be beneficial to provide a strain gauge system which differentiates strain in multiple directions. There is a further need for a strain gauge system which allows large gains of the gauge signal without saturating the output or amplifying noise. Further there is a need for a strain gauge system which has temperature compensation. There is also a need for a strain gauge system that provides high common mode rejection and electronic offset of the outputs.